The formula for the Volume of a cylinder is
V=pi(d)(h)
So first, to find the diameter, you multiply the radius by 2, since the radius is half the diameter.
Next you plug in all the information you have.
V=pi(4)(20)
For the next step I used a calculator for pi and for precision on my calculations... then my answer was:
V=251.327412287...
So I rounded to the nearest tenth and got:
V=251.3
